Tractor with narrow body portion providing increased traction from side-by-side driven rear wheels

ABSTRACT

A tractor of width acceptable for highway travel having a narrow rear body portion between the rear wheels, the width of the body portion being less than the width of each pneumatic tire mounted on the rear wheels. Four or six rear tires which are rotatable on the same axis have the narrow body portion disposed centrally and closely between them, such body portion extending forwardly relatively to the rear wheels with the forward portion of the body, which is substantially wider than the rear portion, mounting an engine near the front wheels. A power transmitting linkage connects the engine with the rear wheels through the rear body portion which, with lateral projections, houses a differential and the necessary shaft bearings. A lifting device extends rearwardly from the rear body portion to behind the rear wheels and then extends laterally where it functions to scrape mud or the like from the treads of the rear tires. A tow bar also extends aft from the rear body portion which is sufficiently wide to scrape mud or the like from the interior sides of the closest rear wheels.

This application is a continuation of application Ser. No. 653,513filed, Jan. 29, 1976.

SUMMARY OF THE INVENTION

The invention relates to tractors comprising an engine and front andrear ground wheels.

According to the invention the engine is located in advance of the frontwheels with respect to the intended direction of forward travel of thetractor, the front and rear wheels being relatively pivotable about asubstantially vertical axis that is positioned between them, and whereina lifting device is provided at substantially the rear of the tractorwith respect to said direction.

For a better understanding of the invention, and to show how the samemay be carried into effect, reference will now be made, by way ofexample, to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an agricultural tractor in accordance with theinvention,

FIG. 2 is a side elevation of the tractor of FIG. 1,

FIG. 3 is a front elevation as seen in the direction indicated by anarrow III in FIG. 2,

FIG. 4 is a rear elevation as seen in the direction indicated by anarrow IV in FIG. 2,

FIG. 5 is a partial rear elevation, to an enlarged scale, of the tractorof FIGS. 1 to 4, the tractor being illustrated in operation with oneground wheel in a plowed furrow,

FIG. 6 is a partial-sectional plan view, to an enlarged scale ascompared with FIGS. 1 to 4, of a rear central region of the tractor ofFIGS. 1 to 5,

FIG. 7 is a plan view that is similar to FIG. 1 but illustrates certainmodifications to the tractor of FIGS. 1 to 6,

FIG. 8 is a plan view of an alternative agricultural tractor constructedin accordance with the invention, and

FIG. 9 is a side elevation of the tractor of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 6 of the drawings, those Figures illustrate anagricultural tractor but it is emphasized that this is purely by way ofexample and that the invention is equally applicable to a tractor thatis intended for non-agricultural purposes. The tractor has a bodyincluding a frame that is generally indicated by the reference numeral1, said frame 1 comprising a substantially horizontal beam 2 that issubstantially parallel to the intended direction of forward travel ofthe tractor as indicated by an arrow A in FIGS. 1 and 2 of the drawings.The rear end of the frame beam 2 with respect to the direction A issecured to the housing of a torque converter 3 whose rear, in turn, issecured to the housing 4 of a differential. The output shafts of thedifferential carry rear driven ground wheels 5 whose arrangement will bedescribed in greater detail below. Smaller front ground wheels 6 areindirectly connected to the frame beam 2 near the leading end of thatframe beam in a manner which will also be described in greater detailbelow. The tractor has an engine 7 which, in the example that is beingdescribed, is an internal combustion engine rated at not less thansubstantially 100 horsepower, said engine 7 being mounted on top of theframe beam 2 at a location in front of the torque converter 3 so as tolie at a horizontal level above that of the tops of the front groundwheels 6 with at least part of the engine as far advanced in thedirection A as are the front ground wheels 6.

A hydraulic mechanism 8 which operates a rear-mounted three-pointlifting device or hitch 9 of the tractor is arranged on top of thedifferential housing 4 at substantially the rear of that housing withrespect to the direction A. The lifting device or hitch 9 comprises twoupper arms 10 that are located alongside one another in horizontallyspaced apart relationship, the arms 10 being turnable upwardly anddownwardly about the aligned axes of corresponding shafts 11. Thealigned axes of the two shafts 11 extend substantially horizontallyperpendicular to the direction A and are turnable by the hydraulicmechanism 8, in a manner that is known per se, to raise or lower theupper arms 10 as may be required. The free rearmost ends of the upperarms 10 are pivotally connected to the upper ends of corresponding rods12, the lower ends of those rods being pivotally connected, in turn, tolugs that are located between the ends of corresponding lower liftinglinks 13. In the embodiment which is being described, said lugs aredisposed substantially midway along the lengths of the two lower liftinglinks 13. The leading ends of the links 13, with respect to thedirection A, are turnably connected by substantially horizontallyaligned pivot pins 14 to lugs that are carried by the differentialhousing 4, the axis that is defined by the pivot pins 14 beingsubstantially perpendicular to the direction A.

The top of a housing of the hydraulic mechanism 8 carries a pair ofsubstantially symmetrically identical supports 15 which supports extendobliquely upwardly and rearwardly away from said housing to terminate ata height above ground level which is substantially equal in magnitude tothe diameter of one of the rear driven ground wheels 5. The upper rearends of the two supports 15 are rigidly interconnected by a horizontallydisposed beam 16 which extends substantially perpendicular to thedirection A throughout nearly the whole width of the tractor (see FIG.1). As seen in plan view (FIG. 1), the beam 16 is located behind thecommon axis of rotation of the rear driven ground wheels 5, said beam 16supporting a platform 17 that extends forwardly therefrom relative tothe direction A. The platform 17 forms part of the bottom of a drivingcabin 18. A rear portion of the platform 17 is substantiallyhorizontally disposed but, at a location which is just in front of thecommon axis of rotation of the rear ground wheels 5 with respect to thedirection A, the platform is bent over obliquely downwardly and, at itsfront, forms a lower cabin floor portion 19 at the foot of opposite sidedoors 20 of the cabin. A front wall 21 of the driving cabin 18 has alarge central window (FIG. 3) and is located immediately in front of theleading hinged edges of the two side doors 20, those doors 20 also beingprovided with windows throughout most of their respective areas. Accessladders 22 that each comprise four rungs are arranged beneath the twoside doors 20 with the upper rungs thereof at substantially the level ofthe lower cabin floor portion 19. The upper edge of the front wall 21 ofthe cabin 18 is connected to a cabin roof 23 and the rear edge of saidcabin roof is connected to a rear wall 24 of the cabin. The side doors20 of the cabin 18 are located in side walls 25 thereof and it will benoted from the drawings that the rear wall 24 and side walls 25, likethe side doors 20 and the front wall 21, are provided with windowsthroughout the greater parts of their respective areas.

A frame 26 is located inside the driving cabin 18 and carries a drivingseat 27, a steering wheel 28 and other control members for the operationof the tractor. The platform 17 carries an upright pivot 29 and theframe 26, together with the parts which it carries, is turnable aroundthe pivot 29 on the platform 17 between the position illustrated in FIG.2 of the drawings in which a person occupying the seat 27 will faceforwardly in the direction A and an alternative position, that is turnedthrough 180° about the axis of the pivot 29, the alternative positionbeing such that a person occupying the seat 27 will face rearwardly withrespect to the direction A and towards the window in the rear wall 24 ofthe cabin 18. Means that is not illustrated in the drawings is providedto enable the frame 26 to be retained in either of the two alternativepositions about the pivot 29 that have just been described. As seen inplan view, the whole of the frame 26 is located behind the lower cabinfloor portion 19, with respect to the direction A, in either of the twoalternative positions of use thereof. The driving cabin 18 has a widthwhich is preferably not less than 1.5 meters and not greater than 1.8meters and, with such a transverse dimension, that part of the interiorof the cabin 18 that is disposed between the side doors 20 is sufficientto accommodate a person standing upright where the view of the driveroccupying the seat 27 will not be impeded in substantially the directionA to any disadvantageous extent. The distance between the lower cabinfloor portion 19 and the cabin roof 23 is great enough to enable anyonewho is not unusually tall to stand without stopping and, if such aperson stands to the side with respect to the direction A, hisinterference with the driver's view in that direction will be at aminimum. The driving seat 27 is located wholly above the level of thetops of the rear driven ground wheels 5 and the lower cabin floorportion 19 is located immediately above the top of the differentialhousing 4, such portion being spaced above ground level by a distancewhich is substantially 75% of the diameter of one of the rear drivenground wheels 5.

There is, in fact, a row of four of the rear driven ground wheels 5which are individually designated in the drawings by the references 30,31, 32 and 33. The four wheels 30 to 33 are arranged in two pairs thatare disposed at opposite sides of a vertical plane of substantialsymmetry of the tractor which extends in the direction A. The four rearwheels 30 to 33 all form part of the original equipment of the tractor,that is to say, none of them is furnished as an "optional extra". Thepair of wheels 30 and 31 that is located at one side of the imaginaryplane of substantial symmetry of the tractor that has been referred toabove has the two wheels rigidly secured to one another and the same istrue of the two wheels 32 and 33 of the pair located at the oppositeside of the imaginary plane. Due to the provision of the differentialwhich will be described in greater detail below, the pair of wheels30/31 or 32/33 that is at the outer convex side of a bend negotiated bythe tractor during its travel can rotate at a faster speed than theother pair disposed at the inner concave side of that bend. The overallwidth of the row of four wheels 30 to 33 in a horizontal direction thatis substantially perpendicular to the direction A is preferably notgreater than 3.0 meters and, in the embodiment which is being described,said width has a magnitude of substantially 2.5 meters. Each of thewheels 30 to 33 has a pneumatic tire whose tread width in the samedirection as that which has just been mentioned is preferably not lessthan 35 centimeters and not more than 50 centimeters, a tread width ofsubstantially 45 centimeters being advantageous. The spacing between thetires of the wheels 30 and 31 of one pair and between the tires of thewheels 32 and 33 of the other pair is preferably substantially 15centimeters. The distance between the pneumatic tires of the two innerwheels 31 and 32 of the two pairs should not be more than 50 centimetersand a magnitude of between 20 centimeters and 40 centimeters inclusiveis preferred. In the embodiment which is being described, the distancein question is substantially 40 centimeters. Each of the four wheels 30to 33 has an overall diameter which should not be less than 1 meter andwhich is advantageously between 1.4 and 1.8 meters. In the embodimentwhich is being described, each of the wheels 30 to 33 has an overalldiameter of substantially 1.5 meters. It will be seen from FIG. 2 of thedrawings that the driving seat 27 in the cabin 18 is locatedsubstantially vertically above the common axis of rotation of the fourwheels 30 to 33.

As seen in plan view (FIGS. 1 and 6), the width of the frame 1 variessignificantly lengthwise therealong. The parts thereof that are locatedin front of the rear driven ground wheels 5 (said parts comprising thebeam 2, the torque converter 3, the engine 7 and cover plates and thelike 34 therefor) have a width that is substantially the same as thedistance between a vertical plane of symmetry of the wheel 31 thatextends in the direction A and a similar plane in respect of the wheel32. The parts of the frame 1 that are located to the rear of the torqueconverter 3, with respect to the direction A, are of significantly lesswidth than are the parts disposed in front of the differential housing4, the latter being the principal or only component of the parts nowunder consideration. The width of the rear parts of the frame (notincluding projections 48 and 49) 1 is between substantially 30 andsubstantially 45 centimeters inclusive and a width of substantially 35centimeters is preferred so that said parts can fit, as illustrated inthe drawings, between the rear wheels 31 and 32 with sufficient workingclearance from those wheels.

FIG. 6 of the drawings shows that the cover plates or the like 34 forthe torque converter 3 and the engine 7 are located, together with saidtorque converter 3 and engine 7, in front of the foremost extremities ofthe rear wheels 31 and 32 with respect to the direction A. It is notedthat the term "torque converter" is used in a generic sense and isintended to include within its scope such a mechanism as a manuallychangeable gear box. The cover plates or the like 34 are closer to oneanother, relative to the part of the frame 1 that has just beendiscussed in the part of the frame that is disposed between the rearwheels 31 and 32, the spacing therebetween becoming narrower from aregion of the frame that is located approximately in register (as seenin plan view--FIG. 6) with the foremost extremities of the wheels 31 and32 relative to the direction A. The cover plates or the like 34 support,between the wheels 31 and 32, substantially horizontally alignedbearings 35 and 36 that are spaced apart from one another in thedirection A. The bearings 35 and 36 rotatably support an output ordriving shaft 37 of the torque converter 3, the shaft 37 carrying,immediately behind the rear bearing 36, a bevel pinion 38. The teeth ofthe pinion 38 are in driving mesh with those of a crown wheel 39, thecrown wheel 39 being rigid with a rotatable housing 40 in whichsubstantially horizontally aligned output or half shafts 41 and 42 havetheir inner ends rotatably journalled. The inner ends of the two shafts41 and 42 carry, inside the housing 40, corresponding bevel pinions 43and 44, the teeth of both those pinions 43 and 44 being in mesh with theteeth of smaller bevel pinions 45 and 46 that are rotatably mounted inthe housing 40, between the pinions 43 and 44, so as to be capable ofrevolving about a common axis which is rotatably displaceable with thehousing but which is always perpendicular to the axis of rotation of theoutput or half shafts 41 and 42. It will be realized from thedescription that has just been given and from FIG. 6, in particular, ofthe drawings that the differential is of generally known construction.

The shaft 47 extends substantially horizontally beneath the output ordriving shaft 37 in substantially parallel relationship with that shaft,said shaft 47 being rotatably supported by bearings at appropriatelocations in the differential housing 4. The shaft 47 projects from therear of the housing 4 to form a rear power take-off shaft of the tractorat which point it is splined or otherwise keyed to enable it to transmitdrive to the working parts of various rear-mounted tools and implements.The power take-off shaft 47 is driven from the output side of the torqueconverter 3 and its speed of rotation relative to that of the engine 7is therefore dependent upon the gear ratio selected at any particulartime. It should be noted that it is possible for the shaft 47 to bedriven directly from the engine 7 in which case its speed of rotation atany particular time will be the same as that of the output shaft of theengine 7. The differential housing 4 is formed with substantiallysymmetrical lateral projections 48 and 49 whose centers aresubstantially coincident with the common longitudinal axis (axis ofrotation) of the shafts 41 and 42. The projections 48 and 49 accommodatelarge substantially horizontal bearings 50 and 51 for intermediateregions of the shafts 41 and 42. Projections 48 and 49 have flanges atthe inner ends of gently outwardly tapering axle supports 52 and 53rigidly secured to them and it will be seen from FIG. 6 of the drawingsthat outer end regions of the two axle supports 52 and 53 receivefurther substantially horizontal bearings 54 for corresponding regionsof the shafts 42 and 41. The axle supports 52 and 53 are of hollowconstruction and the output or half shafts 41 and 42 which theyrotatably support, with the aid of the bearings 50/51 and 54, havecircular discs 55 and 56 rigidly secured to them in such a way that thegeneral planes of the discs 55 and 56 are perpendicular to the commonlongitudinal axis of rotation of the two shafts 41 and 42. It will benoted that the rear wheels 31 and 32 are arrnged around the axlesupports 52 and 53 respectively, said wheels 31 and 32 having hubportions 57 and 58 which are disposed at the sides of those wheelsremote from the differential housing 4 and which are releasably securedto the corresponding discs 55 and 56 by bolts 59.

The described and illustrated construction whereby the portions 57 and58 of the hubs of the two wheels 31 and 32 project outwardly from thegeneral planes of corresponding sides of those wheels is a substantiallyconventional one for tractors and, with commercially available tractorwheels, the perpendicular distance between the outermost flatsubstantially annular surface of each hub portion 57 or 58 and thegeneral plane of the neighbouring side of the wheel 31 or 32 concernedis substantially 7.5 centimeters. In addition to securing the hubportions 57 and 58 to the discs 55 and 56, the bolts 59 also secureidentical, but oppositely facing, hub portions 60 and 61 of the rearwheels 30 and 33 respectively to the two discs 55 and 56. As will beevident from FIG. 6 of the drawings, the substantially flat annularparts of the hub portions 57 and 58 are sandwiched by the bolts 59between the corresponding parts of the hub portions 60 and 61 and thediscs 55 and 56 respectively. The axle supports 52 and 53 each have anaxial length that is substantially the same as the width (thickness) ofthe pneumatic tire of one of the wheels 31 or 32. Because of theprojecting construction of the portions 57 and 58 of the hubs of thewheels 31 and 32, quite large cavities are formed "inside" those wheelsso that the latter, as briefly mentioned above, effectively surround thecorresponding supports 52 and 53.

A combined towing and scraping member 62 is fastened to the bottom ofthe differential housing 4 and has a width which is substantially thesame as that of the rear part of the frame 1 which comprises saidhousing 4. The member 62 is of plate-like formation and has a leadingsubstantially horizontal portion, which is rigidly secured to thehousing 4, whose length, in the direction A, is substantially the sameas that of the radius of one of the rear driven ground wheels that arecollectively indicated by the reference 5. The member 62 comprises adownwardly and rearwardly inclined portion which (see FIG. 2) commencesat a location just in front of the axis of rotation of the wheels 5 withrespect to the direction A. The rear-most end of the inclined portion issubstantially in line with rear regions of the wheels 5 as seen in sideelevation (FIG. 2) and is there bent over upwardly to form a smallsubstantially horizontal portion in which a hole 63 (FIG. 6) is formedfor towing purposes. The small substantially horizontal portion of themember 62 in which the hole 63 is formed is located at a height aboveground level which has a magnitude of between substantially 30% andsubstantially 40% of the radius of one of the rear wheels 5. The member62 has downwardly bentover stiffening rims 64 (FIG. 5) along the edgesthereof that are generally parallel to the direction A and, since thewidth of said member 62 is substantially the same as that of the housing4, its two rims 64 are very close to the inner side surfaces of thetires of the two wheels 31 and 32. The rims 64 of the member 62 thusperform the scraping function of that member because any significantamounts of mud or the like that may adhere temporarily to the sides ofthe tires in question will be stripped from those sides as they movepast the rims 64. The specified magnitude of the distance of therearmost end of the member 62 above the ground surface is such that,should at least one of the tires of the two wheels 31 and 32 becomepunctured or be seriously underinflated, the bulge that will occur inthe lowermost region thereof will be clear of contact with the member62.

The lower lifting links 13 of the lifting device or hitch 9 are disposedabove the rearmost end portion of the member 62 (see particularly FIG.4) and said member 62 thus also affords a lower stop that limits thepossible downward movement of the links 13. Extreme rearmost ends of thetwo links 13 are bent over outwardly in opposite directions to formsubstantially plate-shaped scrapers 65 that are both disposedsubstantially horizontally perpendicular to the direction A, the outerextremities of said scrapers 65 being located substantially in verticalmedian planes of the tires of the two wheels 31 and 32 that extendparallel to the direction A. It preferred, the extremities of thescrapers 65 may be located even further apart from one another beyondthe median planes that have just been mentioned. The extremities of thescapers 65 carry end plates 66 that are formed with apertures (see FIG.2), said end plates 66 being substantially vertically disposed andsubstantially parallel to the direction A. The leading edges of theplate-shaped scrapers 65 are very close to the treads of the tires ofthe two wheels 31 and 32 respectively and, in most positions of thelifting device or hitch 9, said leading edges are at a higher horizontallevel than are the corresponding rear edges. It will be appreciated thatthe inclinations of the scrapers 65 to the horizontal will vary inaccordance with the angular positions of the lower lifting links 13about the pivot pins 14.

The transverse supporting beam 16 carries two elongated and arcuatelycurved scrapers 67 that are both of channel-shaped cross-section. Eachscraper 67 extends generally perpendicular to the longitudinal axis ofthe beam 16 and is located principally in a corresponding one of the twospaces between the wheels 30/31 and 32/33 respectively. The scrapers 67are orientated downwardly from the beam 16 and the center of curvatureof each arcuately curved scraper is spaced forwardly therefrom withrespect to the direction A. Each scraper 67 is turnable about the axisof a corresponding pivot pin 68, said pivot pins 68 being substantiallyhorizontally perpendicular to the direction A and being mounted near theopposite ends of the beam 16 by support lugs 69. Each pivot pin 68 has acorresponding coil spring 70 wound around it with said springs 70arranged in such a way that one end of each of them is fastened to thebeam 16 while the opposite end thereof secured to the scraper 67concerned at a location spaced from the corresponding pin 68. Thesprings 70 thus tend to maintain the scrapers 67 in predeterminedangular positions about the axes of the pins 68 and to return thescrapers 67 to those positions upon displacement thereof in eitherdirection about the pins 68. Each scraper 67 has a width in a horizontaldirection that is perpendicular to the direction A which is a littlesmaller than is the distance between the relatively facing side surfacesof the pneumatic tires of the rear wheels 30/31 and 32/33 respectively.In the embodiment which is being described, the width of each scraper 67is substantially twelve centimeters. As an alternative to thechannel-shaped cross-section that is illustrated for the scrapers 67,they may each have a I-shaped cross-section.

Brackets 71 (FIG. 3) depend from the frame beam 2 at locations near tothe leading end of that frame beam and carry a strong horizontal pivot72 with an axis which is substantially horizontally parallel to thedirection A, said axis being contained in the aforementioned imaginarysubstantially vertical plane of substantialy symmetry of the tractorthat extends in the direction A. The center of a front axle beam 73 isrockable about the pivot 72 between the brackets 71 and the beam 73 isnormally substantially horizontally perpendicular to the direction A.The axle beam 73 is freely rockable about the pivot 72 and indirectlycarries the front wheels 6. There are two pairs 74/75 and 76/77 of thefront wheels 6, said two pairs being located substantially symmetrically(when they are disposed for straight travel of the tractor) at oppositesides of the imaginary plane of substantial symmetry of the tractor thathas been referred to above. The pair 74/75 of front wheels is angularlysteerable about the substantially vertical axis of an intervening shaft78 and the pair of front wheels 76/77 is steerable in the same way aboutthe similarly disposed axis of a shaft 79. Steering arms 80 and 81 arefastened to the upper ends of the shafts 78 and 79 respectively andextend rearwardly and downwardly (see FIG. 2) therefrom in rearwardlyconvergent (see FIG. 1) relationship. A track rod 82 pivotallyinterconnects the rearmost ends of the two steering arms 80 ad 81 in agenerally known manner and is operatively coupled to the steering wheel28 by parts which are not illustrated in the drawings and which it isnot necessary to describe for the purposes of the present invention. Thelower ends of the two shafts 78 and 79 are fastened to shortsubstantially horizontal housings 83 and 84 respectively, said housingsbeing angularly steerable with the shafts 78 and 79 and each of themaccommodating a corresponding one of the hydraulic motors (notillustrated). Each hydraulic motor drives one of the corresponding pairof front wheels 74/75 and 76/77, the hydraulic motors being suppliedwith oil or other fluid pressure medium from a hydraulic pump that isnot illustrated in such a way that they can rotate at dissimilar speedswhen, for example, the tractor is negotiating a bend.

FIG. 5 of the drawings illustrates the pair of rear wheels 30/31 at oneside of the imaginary substantially vertical plane of substantialsymmetry of the tractor that extends in the direction A. It will be seenfrom FIG. 5 that the pneumatic tires of the two wheels 30 and 31 havedifferent treads. The tire of the outer wheel 30 has oblique tread teeth85 and the tire of the inner wheel 31 has oblique tread teeth 86 but theradial height of each tooth 86 is between twice and three times that ofeach tooth 85. Moreover, the regular circumferential distance betweenthe teeth 85 of the tread of the tire 30 is less than the regulardistance between the teeth 86 of the tread of the tire 31, the teeth 86preferably being spaced apart from one another by substantially twicethe distance between immediately neighboring teeth 85.

FIG. 7 of the drawings illustrates a tractor which is basicallyidentical to the one that has already been described above withreference to FIGS. 1 to 6 of the drawings but in which the arrangementof the rear driven ground wheels 5 is different. The row of four rearwheels 30 to 33 inclusive has an overall width in a directionperpendicular to the direction A of substantially 2.0 meters which isconvenient for travel along public roads and the like. However, when thetractor is to operate in extremely adverse ground conditions, it isadvantageous to employ two additional rear wheels 87 and 88 alongsidethe rear wheels 30 and 33 respectively. The overall width of the rowwhich then comprises six of the wheels 5 is increased to substantially3.0 meters. Each of the two wheels 87 and 88 has a tire width(thickness) of substantially 38 centimeters and distances ofsubstantially twelve centimeters are left between the facing surfaces ofthe tires of the wheels 30/87 and 33/88 respectively. Once again, in theembodiment of FIG. 7, the distance between the tires of the two wheels31 and 32 that are located at immediately opposite sides of thedifferential housing 4 is substantially 24 centimeters. Moreover, outputor half shafts of the differential again project axially throughinternal cavities of the wheels 31 and 32 but, in this case, they alsoproject through internal cavities of the respectively immediatelyneighboring wheels 30 and 33. The additional wheels 87 and 88 at theopposite ends of the row are, when fitted, secured to the wheels 30 and33 in substantially the same manner as has already been described withreference to FIG. 6 of the drawings for the connections between thewheels 30/31 and 33/32. However, it will be noted that, to this end, thewheels 30 and 33 require to be furnished with hub portions that aresimilar to the portions 57/58 and 60/61, at both their opposite sides orto be provided with separate auxiliary hub portions. FIG. 7 illustratesthe provision of single front ground wheels 6 at opposite sides of theframe 1 but it is, of course, possible to provide the wheels 6 in pairsas has already been described with reference to FIGS. 1 to 6 of thedrawings.

In the embodiment of FIG. 7, the towing and scraping member 62 is of adifferent construction to that which has been described above. Arearmost end portion of the member 62 has a scraper 89 rigidly securedto it so as to extend substantially horizontally perpendicular to thedirection A. It will be noted from FIG. 7 that the opposite free ends ofthe scraper 89 are located beyond substantially vertical median planesof the tires of the two wheels 31 and 32 that extend parallel to thedirection A. The member 62 itself once again has the previouslydescribed rims 64 that co-operate scrapingly with the facing inner sidesurfaces of the tires of the two wheels 31 and 32. The extremities ofthe scraper 89 carry end plates 90 that both extend substantiallyvertically parallel to the direction A. The end plates 90 projectrearwardly from the scraper 89 with respect to the direction A and areprovided with substantially horizontally aligned rotatable eyes 91 whichsurround holes to accommodate shafts, bolts or the like that enableconnections to be made to various implements and tools. A lug 92projects rearwardly from the scraper 89 at a location centrally acrossthe width of the tractor and is formed with a hole 93 for towingpurposes, said apertured lug 92 constituting a towing member or hook.When, as illustrated in FIG. 7, only single front ground wheels 6 areprovided, those ground wheels are undriven and serve only supporting andsteering functions.

FIGS. 8 and 9 of the drawings illustrate a tractor having a frame whichcomprises two relatively pivotable portions 94 and 95. The front portion94 with respect to the direction A is turnable relative to the rearportion 95 about the substantially vertical axis of a strong bipartitepivot 96. The front frame portion 94 comprises a hollow beam 98, therearmost end of that beam 98 with respect to the direction A beingfurnished with a fork 97 the limbs of which support the two parts of thestrong pivot 96. The leading end of the beam 98 with respect to thedirection A supports an internal combustion engine 99 of the tractor.The beam 98 is provided, at locations between the pivot 96 and theengine 99, with substantially symmetrically arranged lateral projections100 and 101, said projections 100 and 101 being similar in constructionand function to the previously described projections 48 and 49. Onceagain, a differential is located inside the hollow beam 98 and partiallywithin its projections 100 and 101, said differential being driven froma shaft which extends from the torque converter to the differential. Thetorque converter is coupled to the output of the engine 99 and is notshown in the drawings. Output or half shafts extend coaxially inopposite directions from the projections 100 and 101 and have hubportions of front ground wheels 102 and 103 releasably secured to discsat their outer ends. Two further front ground wheels 104 and 105 arearranged beyond the ground wheels 102 and 103 respectively, theconnections between the hub portions of the wheels 102/104 and 103/105being the same as has already been described with particular referenceto FIG. 6 of the drawings. Thus, the projections 100 and 101 extend intothe internal cavities of the wheels 102 and 103 respectively togetherwith the half shafts or output shafts of the differential. As seen inside elevation (FIG. 9), the strong pivot 96 is located very close tothe rearmost extremities of the row of wheels 102 to 105, with respectto the direction A, the engine 99 being located wholly in front of saidrow of wheels relative to the same direction.

Two tanks 106 and 107 which are arranged to contain liquid fuel for theengine 99 are disposed in symmetrical relationship at the front of thetractor, said tanks being secured to opposite substantially verticalside walls of a housing of the engine 99. The fuel tanks 106 and 107 arethus also located wholly in front of the row of wheels 102 and 105 withrespect to the direction A. The two tanks 106 and 107 project fromopposite sides of the housing of the engine 99 and, as seen in plan view(FIG. 8), each of them is of substantially right-angled triangularconfiguration. As seen in FIG. 8, the "opposite" sides of the trianglescoincide with the substantially vertical side walls of the enginehousing, the "adjacent" sides of the triangles projectingperpendicularly from said side walls at the rear of the "opposite" sidesand the two "hypotenuses" are in forwardly convergent relationship withrespect to the direction A and substantially intersect the "opposite"sides at the fronts of the triangles.

The leading end of the rear frame portion 95 is engaged around thestrong pivot 96 between the upper and lower limbs of the fork 97. Therear frame portion 95 has substantially the same width as does the beam98 that forms part of the front frame portion 94, said width preferablybeing between substantially 20 centimeters and substantially 40centimeters, inclusive. The engine housing that is supported by the beam98 has, as can be seen in FIG. 8 of the drawings, a considerably greaterwidth and parts that are carried by the rear frame portion 95 are alsoof greater width. The frame portion 95, which is of hollow formation, isprovided with substantially symmetrically disposed opposite lateralprojections 108 and 109 close to its rear end with respect to thedirection A. The projections 108 and 109 form part of a differentialhosusing and are similar in construction to the projections 48/49 and100/101 that have been referred to above. The projections 108 and 109extend into internal cavities of two rear ground wheels 110 and 111together with the axle housings of half shafts or output shafts of thelast-mentioned differential. Two further rear ground wheels 112 and 113are mounted alongside the ground wheels 110 and 111 respectively to forma row of four rear ground wheels, the connections between hub portionsof the wheels 110 and 112 and the wheels 111 and 113 being effected inthe same manner as has already been described above with particularreference to FIG. 6 of the drawings. The hollow frame beam thatprincipally affords the rear frame portion 95, together with itsprojections 108 and 109, is substantially the equivalent of thedifferential housing 4 and its projections 48 and 49. Similarly, therear ground wheels 110 and 111 correspond to the rear ground wheels 31and 32 of the first embodiment. It will, however, be noted that, in theembodiment of FIGS. 8 and 9 of the drawings, part of the rear frameportion 95 is disposed between the first row of front wheels 102 to 105inclusive and the rearwardly spaced second row of rear wheels 110 to 113inclusive.

The sizes of the pneumatic tires of the wheels 102 to 105 and 110 and113 and the distances between them may conveniently be the same as hasalready been described with reference to the rear ground wheels 5 of theembodiment of FIGS. 1 to 6 of the drawings or to the embodiment of FIG.7 thereof. The same is, of course, true of the wheels themselves.Similarly, the different tread patterns of the tires of the inner wheels31 and 32 as compared with those of the tires of the outer wheels 30 and33 may advantageously be employed for the inner wheels 102, 103, 110 and111 as compared with the outer wheels 104, 105, 112 and 113. FIGS. 8 and9 illustrate the provision of a rear lifting device or hitch thatincorporates the previously described member 62, the scraper 89 and theapertured end plates 90. However, if preferred, the rear lifting deviceor hitch of the embodiment of FIGS. 8 and 9 of the drawings may alsoincorporate a rear towing hook in the form of the apertured lug 92 thatis illustrated in FIG. 7.

As mentioned above, the output shaft of the engine 99 drives a torqueconverter that is not illustrated and, in turn, the torque converter isarranged to rotate an output or driving shaft 114 that extendssubstantially horizontally rearwardly therefrom. The rearmost end of thedriving shaft 114 is provided with a universal joint 115 the center ofwhich is coincident with the axis that is defined by the separatecoaxial upper and lower portions of the strong pivot 96. The universaljoint 115 is connected to the front of a further driving shaft 116 thatextends rearwardly therefrom into the differential housing from whichthe rear wheels 110 to 113 inclusive are driven. Thus, all eight of theground wheels 102 to 105 and 110 to 113 can be driven simultaneously.

A driving seat 117 is mounted on a frame 118 that also supports asteering wheel 119 and other controls (not illustrated) for theoperation of the tractor. The frame 118 and the parts which it carriesare turnable through substantially 180° about an upright pivot 119 Abetween the position illustrated in FIG. 9 of the drawings in which adriver occupying the seat 117 faces forwardly with respect to thedirection A and a position in which he will face rearwardly with respectto that direction. Means (not illustrated) is provided to retain theframe 118 in either of the two positions that have just been mentioned.In the position of the frame 118 that is illustrated in FIG. 9 of thedrawings, the driving seat 117 is located substantially exactlyvertically above the common axis of rotation of the rear ground wheels110 to 113 inclusive whereas, when the other possible operative positionof the seat 117 is employed, said seat will be located above frontregions of the wheels 110 to 113 inclusive as seen in side elevation andwith respect to the direction A. The seat 117, the steering wheel 119and the other controls (not shown) are enclosed in a driving cabin 120that has a front door (not shown). Access to the front door is by way ofa flight of steps 121 which comprises rungs 122 and 123 that are locatedin a symmetrical manner at opposite sides of the rear frame portion 95and further rungs 124 that are located substantially centrally above theframe portion 95 to terminate near the foot of the front door of thecabin 120. Each of the rear driven ground wheels in each of theembodiments that has been described has an overall diameter which shouldnot be less than substantially 100 centimeters and which isadvantageously between substantially 140 and 180 centimeters. A diameterof substantially 150 centimeters is employed in the examples which havebeen specifically described.

High powered tractors that can exert a strong driving torque on theirdriven ground wheels are often incapable of transforming that drivingtorque wholly into tractive effort since, for example, heavy and/orprolonged rainfall can soften the ground to such an extent that thedriven wheels skid or sink into the soil surface. So-called cage wheelshave been provided alongside driven pneumatically tyred ground wheelsthat are suitable for use on public roads and that form part of theoriginal equipment of the tractor in an effort to extend the area ofcontact between the wheels and the ground surface during operation onsoft land but, although they improve the proportion of the drivingtorque that can be converted into tractive effort, their provisionsubstantially increases the overall width of the tractor to such anextent that it cannot be driven along public roads in most countrieswithout breaking the laws of those countries. Although it is, of course,possible temporarily to remove the cage wheels for public road transportpurposes, this is tiresome and inconvenient when frequent journeys alongpublic roads have to be made. Many known tractors have the disadvantagethat their original standard widths are equal or very nearly equal tothe legally prescribed maximum road transport widths of the countries oforigin so that the addition of driven cage wheels or the like with aview to increasing the area of contact with soft soil when the tractoris in use makes it illegal to drive the tractor along public roads.Without the added driven cage wheels or the like, the area of contactbetween the original wheels and soft soil is insufficient so that thetractor cannot produce enough tractive effort to move many heavyimplements and tools without skiddng, wheel spin or serious sinkage intothe unstable ground surface. Tractors in accordance with the inventionmay have a large area of contact between their tires and the soilsurface so that they can produce a high tractive effort beforesignificant wheel slip or sinkage will occur and this importantadvantage is realized without having an overall tractor width thatinfringes public road transport regulations. The overall width of thatpart of the tractor frame to which the driven wheels are connected isdrastically reduced as compared with conventional tractors so that thereis sufficient space for a row of driven ground wheels with tires, intotal, which have a large area of contact with soft ground andconsequently exert a low pressure upon the ground surface per unit areaof tire in contact therewith. Thus, under all but the most extreme ofadverse conditions, substantially all of the engine torque that isapplied to the driving of the ground wheels can be utilized as tractiveeffort. The maximum permitted width of the tractor (for road transportpurposes) is thus utilized in an optimum manner and a tractor inaccordance with the invention can be used satisfactorily in soilconditions which would render the employment of a conventional tractoreither very difficult and uneconomic or substantially impossible.

The engine 7 of the tractor that has been described with reference toFIGS. 1 to 6 of the drawings drives the shaft 37 by way of the torqueconverter 3, which may be a manual gear box, and said shaft 37 isenclosed in the housing 4 which is no greater in width (thickness) thanone of the tires of one of the driven rear wheels 5. Such width shouldnot be more than substantially 50 centimeters and it is preferred thatit should be within the range of substantially 20 centimeters tosubstantially 49 centimeters. This small width is possible because thedistance between the substantially vertical side cover plates or thelike 34 of the housing 4 is determined principally by the dimensions ofthe bearings 35 and 36 of the shaft 37. Although the portion of thehousing 4 which actually contains the differential is greater in widththan is the remainder of that housing, this does not destroy theadvantages of the invention because the projections 48 and 49 thatpartially contain the differential are entered into the hollow interiorsof the inner ground wheels 31 and 32, such ground wheels beingcommercially available tractor ground wheels that, accordingly, do nothave to be specially-built for employment with tractors in accordancewith the invention. The hub portions 57 and 58 have flat parts that arelocated laterally beyond the general planes of corresponding sides ofthe tires of the wheels concerned and this enables the hub portions oftwo different wheels to be quickly and easily fastened to one another inabutting relationship. The distance between the flat part of each suchhub portion and the general plane of the neighboring side of the tire ofthe wheel concerned is the principal factor in determining the distancebetween the tires of two immediately neighboring wheels of one of therows of such wheels that have been described. However, it is notessential that the hub portions should have the shapes that have beendescribed in regard to the portions 57/58 and 60/61. As an alternative,tractor wheels may be used which have hub portions comprising flat partsthat are substantially coincident with, or located internally behind,the general planes of the sides of tires when fitted to thecorresponding wheels. When such wheels are employed, the tires that arefitted thereon abut against one another in side-by-side relationshipwith substantially no space at all between them except where the housing4 is situated. Apart from that necessary space, substantially the wholeof the prescribed width (for public road transport purposes) of thetractor can be occupied by pneumatic tires and no significant amounts ofmud will be able to penetrate between the abutting tires without theprovision of scrapers.

It can be seen in FIG. 6 of the drawings that it would be possible toincrease the width of the differential by shortening the axle supports52 and 53, the width of said differential being effectively the distancebetween the outermost extremities of the lateral projections 48 and 49of the housing 4. Such an arrangement can be made, when required, and isadvantageous inasmuch as it enables larger and stronger moving parts tobe employed without adding to the overall width of the rear of thetractor provided that the enlarged projections still fit with adequateclearance in the internal cavities of the wheels 31 and 32. Theavailable space is thus used in an optimum manner. In the embodiment ofFIGS. 1 to 6 of the drawings, the tractor has four of the rear drivenground wheels 5 that give an overall width of substantially 2.5 metersand, in addition, has four of the smaller front wheels 6 which latterengage the ground surface with a fairly high pressure because the engine7 is disposed above and between them. The significant pressure withwhich the front wheels 6 engage the ground surface may, as brieflymentioned above, advantageously be utilized in converting the drivingtorque of the engine 7 into tractive effort by arranging hydraulicmotors for the front wheels 6 in the housings 83 and 84.

In the embodiment illustrated in FIG. 7 of the drawings, the transportwidth (without the wheels 87 and 88) is substantially 2.0 meters and theaddition of the wheels 87 and 88 increases that width to substantiallythree meters, the latter being legally allowable on public roads in manycountries and being possible under special licence in others. When thewheels 87 and 88 are mounted in their operative positions as shown inFIG. 7 of the drawings, the tractor has six driven rear wheels.

The tractor that is illustrated in FIGS. 8 and 9 of the drawings haseight driven ground wheels which are arranged in a front row and a rearrow with each row comprising four of the wheels, the overall width ofthe tractor being within the legally allowed limits for travel on publicroads. However, if desired, each of the two rows of four ground wheelsmay have two further ground wheels added to its opposite ends to give atotal of twelve ground wheels arranged in two rows of six wheels each inthe same manner as has already been described with reference to the rearground wheels of the embodiment of FIG. 7. Once again, it is possible todispose a larger than usual number of driven ground wheels within alimited width since the shafts 114 and 116 are inside a narrow framethat has a width of between substantially 20 and substantially 50centimeters, said frame extending from the engine 99, which is locatedat the front of the tractor, rearwardly between the front ground wheels102 to 105 to the differential for the rear ground wheels 110 to 113.The very narrow frame, which is afforded principally by hollow beamsthat accommodate driving shafts, has the advantage that, if required,more than two rows of driven ground wheels could be provided. Thus, inany one of the three embodiments that has been described, a third row offour or six closely adjacent driven ground wheels could be provided thusfurther reducing the pressure per unit area of contact between each tireand the ground surface. Even in very soft or waterlogged soil, sinkagecan thus be reduced to an extent that does not interfere significantlywith operation and it is almost always possible to transform all of theengine output that is available for that purpose into tractive effort.

Generally speaking, the grip of pneumatic tires upon the ground isenhanced if those tyres have tread patterns which exhibit large teethand tractors that are employed in plowing operations are frequentlyfurnished with such tires. However, pneumatic tyres that have treadpatterns with teeth of large radial extent are expensive. Thearrangement shown in FIG. 5 of the drawings can reduce this expensebecause the pneumatic tires of the outermost wheels 30 and 33 of the rowof four wheels 30 to 33 inclusive are tires whose treads have teeth 85of comparatively small radial extent, said teeth being, however,relatively close together around the circumference of the tire. Theteeth 86 of the treads of the tires of the inner wheels 31 and 32 areteeth of relatively large radial extent so that said tires are thus ofthe expensive kind discussed above, the teeth being spaced apart,however, around the circumference of each tire by greater distances thanare the teeth 85 of the tires of the wheels 30 and 33. FIG. 5 of thedrawings illustrates the tractor in use in a plowing operation with oneof the outer wheels 30 travelling in an already plowed furrow whereasthe immediately neighboring wheel 31, that is of the same overalldiameter, travels on unplowed soil immediately to one side of thefurrow. The large teeth 86 of the tire of the wheel 31 penetrate quitedeeply into the soil and can transform all or most of the applied torqueinto tractive effort. The smaller teeth 85 of the tread pattern of thetire on the wheel 30 do not sink into the furrow to any great extent andare quite adequate for the purpose in view thus making it unnecessary toprovide the wheel 30 (or the wheel 33) with a more expensive tire havingthe teeth 86 of larger radial extent. Since the wheel 30 travels in thealready formed furrow, the plow does not need to be markedly offset inposition relative to the path of travel of the tractor and this enablesthe tractor driver to steer a straight course without exerting a strongcorrective effort to one side on the steering wheel 28 because the plowis nearer to the imaginary substantially vertical plane of substantialsymmetry of the tractor that extends in the direction A than isconventional. If the land to be plowed is very soft, with the resultthat the tractor tends to tilt to one side beyond the inclinationillustrated in FIG. 5, the peripheral surface of the tire of the wheel30 from which the teeth 85 project will come into substantially directcontact with the ground surface which latter will then give a greaterdegree of support. Tilting to a dangerous extent is thus prevented.Since the tire of the wheel 30 has a large number of the teeth 85, thetire is able to transform quite a high torque into tractive effort assoon as the teeth 85 in a lower arc of the tire of significant angularextent have penetrated into the soil.

The scrapers 67 between the tires of the wheels 30/31 and those of thewheels 32/33 and also the scrapers that are provided between the tiresof similarly disposed wheels in the other embodiments act to scrape offmud and lumps of soil from the immediately neighboring sides of thetires of the wheels concerned. It can be seen from FIG. 2 of thedrawings that each scraper 67 covers the whole radial extent of the twotires with which it cooperates so that the sides of tires in questionare kept free of large accumulations of mud throughout operation of thetractor. Owing to the arcuately curved formation of the scrapers 67 thatinitially (as seen in side elevation--FIG. 2) extend substantiallyvertically downwards and then forwardly towards the common axis ofrotation of the rear ground wheels, there will be a tendency for mud andthe like scraped from the tires to travel upwardly along the scrapers 67until it moves outwardly beyond the treads of the tires of the wheelsconcerned. Much of the mud will drop away to the ground surface when itreaches this location, or previously, and any that does not do so willbe displaced rearwardly along the bottom of a corresponding curved guide125, said guides 125 being substantially horizontally disposed but, ascan be seen in FIG. 2 of the drawings, initially projecting rearwardlyand upwardly to a small extent from the tops of the correspondingscrapers 67 to terminate in downwardly bent-over portions. The guides125 are rigidly secured to the support lugs 69. The spring-loadedmounting of the scrapers 67 enables them to deflect about thecorresponding pivot pins 68 to avoid damage in the event of, forexample, a stone or the like becoming jammed between the tires of thecorresponding wheels 30/31 or 32/33.

The rims 64 of the towing and scraping member 62 that is rigidly securedto the bottom of the housing 4 lie very close to the inner side surfacesof the tires of the wheels 31 and 32 and mud and the like scraped fromthose side surfaces by the rims 64 will sooner or later drop back ontothe ground surface between the wheels 31 and 32. There is a tendency formud and the like scraped off by the rims 64 to move away from the tiresconcerned towards the center of the member 62 so that, generallyspeaking, when that mud falls back to the ground surface, it will beclear of contact with the tires of both of the wheels 31 and 32. Therims 64 stiffen the plate-shaped towing and scraping member 62 and tendto prevent the bending of the latter when the member is used as a towinghook by employing the hole 63 that is formed therein. In particular, therims 64 tend to prevent upward deflection of the member 62. The scrapers65 that can be seen best in FIGS. 4 and 5 of the drawings are arrangedto shed adhering mud and the like from at least the inner teeth 86 ofthe tires of the two wheels 31 and 32 because the plates 66 at the endsof the scrapers 65 are located in, or just beyond, the median planes ofthe tires of the wheels 31 and 32 that extend parallel to the directionA. The end plates 66 are employed for the connection of implements ortools during the use of the tractor and, if desired, the scrapers 65 canbe extended outwardly beyond them to embrace substantially the whole ofthe width (thickness) of the tire of each of the two wheels 31 and 32.The scrapers 65 cooperate with the treads of the tires of the wheels 31and 32 in the manner of butter curlers and the removed mud curls awaydownwardly and rearwardly behind the scrapers 65 to fall back to theground behind the tires.

In the embodiments of FIGS. 7 to 9 of the drawings, the member 62 is notrigidly secured to the tractor frame 1 but forms part of the rearlifting device or hitch of the tractor, the member 62 being provided atthe back with the scraper 89 which scraper extends effectivelythroughout the width of the treads of the tires of the wheels 31 and 32or 110 and 111. The scraper 89 may be extended laterally, if desired, toco-operate also with the treads of the tires of at least the wheels 30and 33 or 112 and 113. The scraper 89 also serves as a support for theend plates 90 to which an implement or tool can be connected employingthe eyes 91. Scrapers that are substantially identical to the previouslydescribed scrapers 67 may be arranged between the closely neighboringtires of the pairs of ground wheels in the embodiments of FIGS. 7 to 9of the drawings and, in the embodiment of FIGS. 8 and 9, the fork 97that lies between the tires of the wheels 102 and 103 may also carry alaterally disposed scraper (not shown) for keeping the treads of thetires 102 to 104 inclusive clean. As previously mentioned, the rearscraper 89 may be increased in width so that it will co-operate alsowith the treads of the tires of the wheels 112 and 113.

In the embodiment of FIGS. 1 to 6 of the drawings, the engine 7 islocated above and between the front ground wheels 6 so that the pressureof those wheels on the ground is quite high and it can be useful, asdescribed, to arranged them so as to be drivable. However, in order thatthe pressure of the rear wheels 5 upon the ground should not be too low,other parts of the tractor are arranged near to the common axis ofrotation of the rear ground wheels. Thus, the driving cabin 18 and thedriving seat 27 are arranged substantially directly above the axis ofrotation of the rear wheels 5. In the embodiment of FIGS. 8 and 9 of thedrawings, the engine 99 is located in front of the ground wheels 102 to105 with respect to the direction A and thus tends to reduce thepressure of the rear wheels 110 to 113 upon the ground surface. In orderto compensate for this, the driving cabin 120, the driving wheel 117,the controls of the tractor and the rear lifting device or hitch thereofare all located above, or close to, the common axis of rotation of therear ground wheels.

The driving cabin 18 of the embodiments of FIGS. 1 to 7 of the drawingscontains the driving seat 27 and also the cabin floor portion 19 whichis at a lower level. The distance between the cabin floor portion 19 andthe roof 23 of the cabin is such that a person whose height is not morethan substantially 1.75 meters can stand upright in the cabin andpreferably at a location alongside one of the doors 20 so as not toimpede the forward view in substantially the direction A of an operatoroccupying the seat 27.

The front and rear portions 94 and 95 of the frame of the tractor thathas been described with reference to FIGS. 8 and 9 of the drawings arerelatively pivotable about the substantially vertical axis that isdefined by the strong pivot 96 and relative angular displacement of thetwo frame portions 94 and 95 about said axis enables the tractor to besteered from the wheel 119. Vehicle steerability in this general manneris known per se and, accordingly, the parts that enable it to beeffected are not illustrated in FIGS. 8 and 9 of the drawings and do notneed to be described for the purposes of the present invention. Theoverall diameter of each of the wheels 102 to 105 and 110 to 113 of thetractor of FIGS. 8 and 9 of the drawings, as previously indicated, issubstantially 150 centimeters and the tractor, when equipped with eightground wheels as illustrated, has an overall width which is not greaterthan 3.0 meters and which is preferably substantially 2.5 meters. Thetractor can thus travel along public roads without restriction.

Although various features of the tractors described or illustrated orboth in the accompanying drawings will be recited in the followingclaims as inventive features, it is emphasized that the inventiveconcepts disclosed herein are not necessarily limited to those features,but include within their scope each of the parts of each tractor thathas been described, or illustrated or both in the accompanying drawingstaken individually and in various combinations.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:
 1. A tractor whichcomprises: a body including a frame therefor, said body having a narrowrear portion and a wider front portion; front and rear groups of groundengaging wheels, said front group of wheels including at least two frontwheels mounted from said front body portion whereby one said front wheelis disposed laterally on each side of said front body portion; an enginemounted on said front body portion; said rear group of wheels comprisingat least four wheels mounted on said rear body portion with at least twowheels on each side thereof, all said rear wheels of said group havingthe same axis of rotation, pneumatic tires mounted on at least two ofsaid rear wheels on opposite sides of said rear body portion, said rearbody portion including a part extending from the circumference of saidrear wheels forwardly to join said forward body portion, the maximumwidth of said rear body portion at the location of said part thereofproximate the circumference of said rear wheels being less than thewidth of each of said pnumatic tires; a power linkage from said engineto said rear wheels extending through said body; and a lifting device atthe rear of said rear body portion extending therefrom to behind saidrear wheels.
 2. A tractor in accordance with claim 1 wherein said groupof rear wheels consists of six wheels.
 3. A tractor in accordance withclaim 2 wherein the maximum width of the tractor does not exceed aboutthree meters.
 4. A tractor according to claim 1, wherein two said groundwheels in a group of said ground wheels are spaced apart from oneanother by a distance of substantially forty centimeters, a combinedtowing and scraping member being provided which is disposed in the spacebetween them.
 5. A tractor according to claim 1, wherein two said groundwheels in said rear group of said ground wheels are spaced apart fromone another by a distance of substantially forty centimeters, saidlifting device being disposed between them.
 6. A tractor according toclaim 1, wherein two said ground wheels in a group of said ground wheelsare spaced apart from one another by a distance of substantially fortycentimeters and a power take-off shaft of the tractor is disposedbetween them.
 7. A tractor according to claim 1 wherein differentialmeans is housed in said rear body portion between said wheels.
 8. Atractor according to claim 1 wherein the overall width of said frontgroup of wheels is not greater than the overall width of said rear groupof wheels.
 9. A tractor according to claim 1 wherein the maximum widthof said rear body portion at said part proximate the circumference ofsaid rear wheels is not more than twenty percent of the overall width ofsaid rear group of wheels.
 10. A tractor according to claim 9 whereinthe ratio of the width of each said pneumatic tire to the width of saidrear body portion at said location is a number between one and 2.5 to 1.11. A tractor according to claim 9, wherein the maximum width of saidrear body portion at said location is about sixteen percent of theoverall width of said rear group of wheels.
 12. A tractor in accordancewith claim 11 wherein the maximum width of the tractor does not exceedabout two and one-half meters.
 13. A tractor according to claim 9,wherein the maximum width of said rear body portion at said location isabout eighteen percent of the overall width of said rear group ofwheels.
 14. A tractor which comprises: a body including a frametherefor, said body having a narrow rear portion and a wider frontportion; front and rear groups of ground engaging wheels, said frontgroup of wheels including at least two front wheels mounted from saidfront body portion whereby one front wheel is disposed laterally on eachside of said front body portion; an engine mounted on said front bodyportion; said rear group of wheels comprising at least four rear wheelsmounted on said rear body portion with at least two wheels on each sidethereof with the two central wheels thereof mounted proximate said rearbody portion, the overall width of said front group of wheels being notgreater than the overall width of said rear group of wheels, all of saidrear wheels of said group having the same axis of rotation, pneumatictires mounted on said two central rear wheels on opposite sides of saidrear body portion, the maximum width of said rear body portion extendingbetween said rear wheels being less than the width of each saidpneumatic tire, said two central wheels having pneumatic tires mountedthereon being spaced apart a distance not greater than the width of eachsaid pneumatic tire, said maximum width of said rear body portion beingless than twenty percent of the overall width of said rear group ofwheels, a power linkage from said engine to said rear wheels extendingthrough said body; said power linkage including differential means whichis housed in said rear body portion between said rear wheels, wherebythe tractor is so constructed to provide maximum traction force withinsubstantially the maximum width for travel on public roads; and alifting device extending from the rear of said rear body portion tobehind said rear wheels.
 15. A tractor according to claim 14, whereinsaid body portion that is located between said ground wheels in saidrear group has a width of substantially thirty-five centimeters.
 16. Atractor according to claim 14, wherein said portion that is locatedbetween said ground wheels in said rear group accommodates asubstantially horizontal driving shaft for a group of said ground wheelsand at least part of a differential for said last mentioned group ofground wheels.
 17. A tractor according to claim 14, wherein said rearportion located between said ground wheels in said rear driven group isprovided at least one side with a projection in which is accommodated byat least one mechanism in the power linkage between said engine and saiddriven group of wheels.
 18. A tractor according to claim 17, wherein atleast some wheels in said driven group of wheels have hubs which definecavities that open inwardly towards said frame, and wherein saidprojection is located at least partly in one of said cavities.
 19. Atractor according to claim 18, wherein each said cavity accommodates atleast part of a half shaft for driving at least the wheel having suchcavity.
 20. A tractor according to claim 14, wherein at least somewheels in said driven group of wheels have hubs which define cavitiesthat open inwardly towards said frame.
 21. A tractor according to claim20, wherein each said hub comprises a substantially flat portion whichis located outwardly from the center of its corresponding wheel beyond aplane containing one side surface of a pneumatic tire mounted on suchwheel.
 22. A tractor comprising an engine and front and rear groundwheels, six of said ground wheels being drivable wheels each having anoverall diameter of not less than substantially ninety-one centimeters,said six drivable ground wheels being arranged in side-by-siderelationship, power linkage means from said engine to said drivablewheels, said power linkage means including differential means betweenthe central two wheels of said drivable wheels, a body for mounting saidwheels, said body including a portion between said two central wheelswhich contains said differential means to rotate about a single axis,the path of travel of the tractor having a width of substantially twohundred eighty centimeters and pneumatic tires mounted on each of saidsix wheels having a width of substantially thirty eight centimeterswhereby the tractor is adapted to provide substantially maximum tractionwithin its said width.
 23. A tractor comprising an engine, front groundwheels and six driven rear ground wheels arranged in a row inside-by-side relationship, power linkage means from said engine to saiddrivable wheels, said power linkage means including differential meansbetween the central two wheels of said drivable wheels, a body mountingsaid wheels, said body including a rear portion having a width notgreater than that of any rear ground wheel, said rear portion housingsaid differential means, each said rear ground wheel having an overalldiameter of not less than ninety-one centimeters and the overall widthof said row of ground wheels being substantially two hundred eightycentimeters, whereby the tractor is so constructed to providesubstantially maximum tractive force within such overall width.